The invention relates to an electron-beam evaporator for vacuum coating apparatus as used, for example, in optics for tempering lenses or eyeglass lenses. For this purpose the substrates to be coated are moved on an appropriate substrate holder over the vapor source heated by the electron beam, and are thus coated. The evaporation point from which the vapor is released is usually off-center from the main axis of rotation of the substrate holder.
The multiplicity of different substrate shapes and surface curvatures call for special efforts to achieve the desired coating thickness tolerances and coating thickness distribution within a batch on the substrate holder in the vapor coating apparatus. Another difficulty consists in the various evaporation characteristics of the coating material in use. For this reason it is desirable to have a variable or adjustable positioning of the evaporation point with respect to the substrates being coated, so that an optimum evaporator position can be set for each substrate from and each coating material.
An electron beam gun that is movable within the vacuum is disclosed is German Auslegachrift 2I 18 082. A container to which the electron gun is fastened is connected to the atmosphere through a tube. The electron gun is part of the container wall. The tube is guided in the chamber wall and is longitudinally displaceable. Such an apparatus is not suitable for use in optical coating, since it is too expensive. The variable range for the positioning of the evaporation point in optical coating apparatus of the prior art is only around 0.05 to 0.5 m. Furthermore, the vapor coating of the tube and contamination of the optical coating by the hydraulic oil are troublesome.
In DE 28 49 933 an electron beam evaporator is described, which is composed of the three elements: radiation source, deflecting magnet and the mounting for the material to be evaporated. The three component elements are displaceable in their spacing from one another, so that the evaporator is adaptable to the particular application.
In DE 37 04 505 an insertion device for vacuum apparatus is described, which has a bipartite, jointed lever arm the inner part of which is configured as a gas-tight hollow body and contains the driving means for moving the insertion arm.